annoying engine vibration at 3900 - 4500 RPMS

[duaneage]

See if you are missing rubber bumpers on the seat bottom, or if they are too hard. maybe a replacement part is in order.

I like that corbin seat BTW, you should stick with it

[gearhead13]

I have something new to report on my case.
Even though my license plate was amplifying the vibration, it was still there and quite annoying. So, I thought I would do a carb sync today. It was pretty good at idle, just a minor adjustment. But when I cracked the throttle a little, the 2 right cylinders pulled a fair amount more vacuum. So, I adjusted them so they were more equal with the throttle cracked. Went for a ride and the vibration is gone and unnoticable at the 4k rpm range. RELIEF!!

[sedelen]

My '82 GS1100EZ had a nasty vibration noise from about 3,800 to 4,500 rpm, right at my cruise speed in 5th gear. I have stock pipes and thought the baffle on the left side came loose.
Luckily, it was the heatshield. I got my bike with those missing and I found a pair and put them on. It's held by 4 mounting screws. I managed to get 3 on each pipe without too much of a problem, but that 4th one,
front and top of each shield, I've decided you can't get a screw in it unless you take the pipes off. And I decided I'm not going to drop the pipes for that, I mean screw it! so, I found some nylon, telflon washers and zip tied them to the hole on the heat sheild, now the post the screw fits in on the pipe is resting against the nylon/teflon washers and tie straps, no more noisy vibration, now the bike is quiet, I'll see how it holds up.

[maro]

another update. I was wrong. While my corbin does eleminate some of the vibration, it's not gone. I also took off all the side release levers on my stock seats and that helped a bit as there is less rattling. But I can still feel that roughness at 3800 - 4300... which is also cruising speed for me in 5th. 60-65 ish. I have an extra set of carbs I might have TCK clean and set to stock and see if maybe my carbs are the issue. BTW, I checked for twisted crank and it's not twisted.